Not sure what DirecTV dish you're using. I was wondering if that particular dish has the adjustment ring on the rear on the dish. I have several DirecTV dishes that were used for internet and when I set mine up for Galaxy 19, I set the adjustment to zero and then set the skew at the LNBF.
This makes it easier to locate the signal. I am not familiar with the Viewsat receiver, but in the setup menu, there should be a signal meter showing the signal level and quality. Once you get the Lo frequency set, you should be able to play with the elevation and azimuth to find the signal.
It's also a good idea to program in the 12152 H 20000 information KE4EST gave you before starting the process so you have an active channel to work with. If you still have the old LNBF that was on the dish, you could stick it back on, and then take some measurements to see what the focal distance was on the primary LNBF in order to know where to set the new one.
I also measured from the mounting arm to the center of the LNBF to make sure the new one is properly mounted to get the best signal. This way you have the focal distance and how far the center of the old LNBF was from the mounting arm to have two measurements to work with.
Once you get the first one going, the next one will be a lot easier.